While many businesses assume that accountants are bound by generally accepted accounting practices and that these are inviolate, nothing could be further from the truth. Everything is subject to interpretation, and GAAP is no different. For one thing, GAAP themselves permit alternative accounting methods to be used for certain expenses and for revenue in certain specialized types of businesses. For another, GAAP methods require that decisions be made about the timing for recording revenue and expenses, or they require that key factors be quantified. Deciding on the timing of revenue and expenses and putting definite values on these factors require judgments, estimates and interpretations.